Fix markdown code blocks not rendering in HTML

The code blocks are still not rendering properly in HTML. This is my second attempt to fix that.

Author: mpilgrem

doc/maintainers/msys.md

@@ -25,11 +25,8 @@ the steps required to upgrade the MSYS2 version used by Stack.
     that does (using its `pacman` tool). Using the existing Stack-supplied
     MSYS2, in PowerShell and located in a folder with write permissions (so the `.tar.xz` file can be created):
 
-    ```
-    stack exec -- pacman -S tar
-
-    stack exec -- tar cJf msys2-YYYYMMDD-x86_64.tar.xz C:\msys64
-    ```
+        > stack exec -- pacman -S tar
+        > stack exec -- tar cJf msys2-YYYYMMDD-x86_64.tar.xz C:\msys64
 
 4.  Create a new release tagged and named `msys2-YYYYMMDD` in the `master`
     branch of the [commercialhaskell/stackage-content](https://github.com/commericalhaskell/stackage-content)
@@ -39,28 +36,24 @@ the steps required to upgrade the MSYS2 version used by Stack.
     file, to switch over to using the newly uploaded files. For example
     (extract):
 
-    ```
-    # For upgrade instructions, see: https://github.com/commercialhaskell/stack/blob/stable/doc/maintainers/msys.md
-    msys2:
-        windows32:
-            version: "20200517"
-            url: "https://github.com/fpco/stackage-content/releases/download/20200517/msys2-20200517-i686.tar.xz"
-            content-length: 79049224
-            sha256: 9152ddf50c6bacfae33c1436338235f8db4b10d73aaea63adefd96731fb0bceb
-        windows64:
-            version: "20220503"
-            url: "https://github.com/commercialhaskell/stackage-content/releases/download/msys2-20220503/msys2-20220503-x86_64.tar.xz"
-            content-length: 93835868
-            sha256: c918f66e984f70add313ee3a5c5b101132cd93d5a3f8e3555e129e2d3dcb3718
-    ```
+        # For upgrade instructions, see: https://github.com/commercialhaskell/stack/blob/stable/doc/maintainers/msys.md
+        msys2:
+            windows32:
+                version: "20200517"
+                url: "https://github.com/fpco/stackage-content/releases/download/20200517/msys2-20200517-i686.tar.xz"
+                content-length: 79049224
+                sha256: 9152ddf50c6bacfae33c1436338235f8db4b10d73aaea63adefd96731fb0bceb
+            windows64:
+                version: "20220503"
+                url: "https://github.com/commercialhaskell/stackage-content/releases/download/msys2-20220503/msys2-20220503-x86_64.tar.xz"
+                content-length: 93835868
+                sha256: c918f66e984f70add313ee3a5c5b101132cd93d5a3f8e3555e129e2d3dcb3718
 
     The `content-length:` key's value is the size of the file in bytes. It can
     be obtained from the `Length` field of the `dir` command. The `sha256:`
     key's value can be obtained from the command (in PowerShell):
 
-    ```
-    (Get-FileHash msys2-YYYYMMDD-x86_64.tar.xz -Algorithm SHA256).Hash.ToLower()
-    ```
+        > (Get-FileHash msys2-YYYYMMDD-x86_64.tar.xz -Algorithm SHA256).Hash.ToLower()
 
     The `sha256:` key only accepts lowercase hash results as values.
 
@@ -72,9 +65,8 @@ the steps required to upgrade the MSYS2 version used by Stack.
 
     * executing the command:
 
-      ```
-      stack setup --setup-info-yaml <path to local copy of stack-setup-2.yaml>
-      ```
+
+          > stack setup --setup-info-yaml <path to local copy of stack-setup-2.yaml>
 
     If all is well, the command should proceed to download the updated version
     of MSYS2 that has been specified.